Japan tsunami and earthquake - Sunday 13 March

• Up to 10,000 feared dead in Miyagi prefecture aloe
• Cooling system fails at a second nuclear plant
• Japan PM: 'worst crisis since second world war'
• 190 people exposed to radiation
• Original quake upgraded to magnitude 9
• Over 250 aftershocks so far

8.19am: Good morning, we're continuing our live coverage as Japan tackles the aftermath of Friday's devastating 8.9 magnitude earthquake and the ensuing tsunami. Tokyo has doubled the number of rescuers to 100,000 and is still struggling to control the crisis at two nuclear power stations.

The developments today:•Up to 10,000 people may have died in Miyagi prefecture, a police official there has told broadcaster NHK. Miyagi was the area worst-hit by the double disaster. The previous estimate of the death toll was around 1,800, although police had said they were unable to make contact with 9,500 people in the devastated town of Minamisanriku.

8.31am: One very welcome piece of good news: astonishingly, a 63-year-old man was rescued after his home was swept 15km out to sea by the tsunami, Japanese media are reporting. Rescuers in a helicopter spotted him waving from the rooftop near Futabacho, Fukushima prefecture.

8.40am: These remarkable interactive graphics from ABC in Australia and the New York Times use before-and-after pictures of the disaster zone to demonstrate the extent of the devastation.

A Maritime Self-Defence Force destroyer rescued 60-year-old Hiromitsu Shinkawa after discovering him floating on a piece of roof in waters off Fukushima Prefecture, two days after the disaster struck.

The man, from the city of Minamisoma which has been virtually obliterated, was swept out along with his house after the massive tsunami tore into Japan's northeast following a 8.9-magnitude earthquake on Friday.

He is conscious and in "good condition" after his rescue which took place around 12:40 pm (0340 GMT), ministry officials said, adding that he was transported to hospital by helicopter.

"I ran away after learning that the tsunami was coming," Shinkawa told rescuers according to Jiji Press.

"But I turned back to pick up something at home, when I was washed away. I was rescued while I was hanging to the roof from my house."

9.19am: Our correspondent Jonathan Watts is in Shiontona, Miyagi prefecture. He has been speaking to survivors of the tsunami.

Ben McMillan/Guardian

One woman, Harumi Watanabe said she rushed home from work to save her elderly parents but was unable to get them out of the house quickly enough. "There wasn't time to save them. They were old and too weak to walk so I couldn't get them in the car in time," she said.

When the wave hit the house, her mother and father were ripped from her grasp and dragged under-water. "I stood on the furniture, but the water came up to my neck. There was only a narrow band of air below the ceiling. I thought I would die," said Watanabe.

Early indications are that older people will make up a high proportion of the dead because they were unable to act on the tsunami warnings in time. "There are many old people here. We have evacuation drills, but people could not get to the meeting place in time. The tsunami was beyond our expectations. We must reflect on our shortcomings," said Jiro Saito, head of the local disaster countermeasures committee.

Watts reports that further round the coast in Minami Shirazu, close to 10,000 people are reportedly missing after the town was engulfed by the tsunami. The full story will be online shortly.

9.36am: In a a small indication of the massive relief effort now underway, Tokyo vice-mayor @inosenaoki says 44,000 meals of crackers, 643,000 of instant rice and 57,000 units of condensed milk are on their way to the disaster area, along with 384,000 blankets and 9000 portable toilets.

9.39am: Japan's Daily Yomiuri has this powerful eyewitness piece on the "hellish sight" of Kesennumma in Miyagi prefecture, hit by quake, tsunami and fires:

Black smoke belched from fires that continued to spread even after daybreak in this city on the Sanriku Coast with a population of 75,700.

All but the platform of Minami-Kesennuma Station on the JR Kesennuma Line was swept away by tsunami as if it had never existed.

Also hit by tsunami, the city's central community center near the station was flooded to the second-floor ceiling, forcing people evacuated there to stay overnight on the third floor, community center officials said.

Many wrecked cars and trucks lay amidst heaps of rubble, while broken houses were swept down the Okawa river along the JR line. The water continued to ebb and flow with waves from the sea.

A soldier carries an elderly man to a shelter in Natori city, Miyagi prefecture, after the Japanese earthquake and tsunami. Photograph: Str/AFP/Getty Images

9.47am: Justin McCurry in Tokyo reports that Japan's meteorological agency on Sunday upgraded last Friday's earthquake from magnitude 8.8 to 9.0, although it is still referring to this estimate as an "interim value". It occurred 130km off the Pacific coast of Tokoku region at a depth of 24km. It is advising people to be vigilant for further tsunamis, landslides and further building collapses.

It is also warning that there is a 70% chance of a magnitude-7 aftershock striking the country in the next three days.There will be a 50% risk over the three subsequent days.

A satellite image of Fukushima Daichi nuclear power plant after it had been damaged by the earthquake. Photograph: Getty Images

10.40am: The Tokyo Electric Power Company which operates the Fukushima Daiichi and Fukushima Daini nuclear power stations has confirmed that a crane operator has been killed at the Daini plant. The operator was trapped in the crane operating console of the exhaust stack and was transferred to the ground at 5:13pm on Saturday and confirmed the death at 5:17pm.

British nationals in Japan who require assistance should contact the Foreign Office helpline in London: +44 20 7008 0000 (from Japan) or 020 7008 0000 (in the UK). You can also e-mail the Foreign Office on japan.earthquake@fco.gov.uk or skype (text not call) on "fcojapan".

It has issued the following information about the status of Japanese airports:

11.13am: Associated Press is reporting that Japan's prime minister has called the disaster the worst crisis since World War II when two nuclear bombs were dropped of Hiroshima and Nagasaki. He has urged country to unite.

11.33am: Japanese prime minister Naoto Kan has urged Cabinet members to ensure "maximum efforts" are made to save as many people as possible, Kyodo news agency has reported.

He has also met the heads of the Tokyo Electric Power Company, which runs the Fukushima nuclear plant, and Toshiba, which supplied some of the equipment used in the facility, to discuss the crisis.

Electricity providers have warned that consumers could face a week or more of rolling electricity black-outs from tomorrow, due to the shortages caused by shutting down power plants. "There is a high possibility that service areas of Tokyo Electric and Tohoku Electric will face an abnormal situation in which a great deal of supply shortage will occur,'' the industry minister Banri Kaieda told reporters. His ministry has urged large firms to restrict their use of air conditioning, neon lighting and hot water to help conserve the supply.

Chief Cabinet Secretary Yukio Edano has said the government will use its contingency funds of some 200bn yen ($2.44bn) to pay for the relief effort. But Kyodo says the president of the opposition Liberal Democratic Party has said it will meet the government to discuss a possible temporary tax increase to fund relief work.

The nearby bay is filled with cars, concrete and half-sunken homes that have floated away from their foundations. A railway line has been ripped from the ground and twisted vertically like a garden fence. Cars and motorbikes lie broken and so roughly re-parked by the tsunami that some balance precariously on their bonnets. Emergency and media helicopters buzz overhead and the bereaved sob by the side of the road. The air is rich with the rotting smell of disaster and death.

Self-defence force personnel and rescue workers search for bodies amid the the mud. Their work is sporadically interrupted by earthquake alerts and tsunami warnings, but they do not have to look far.

When found the dead are wrapped in blue tarpaulins and laid on military stretchers. In Shintona their numbers rose as quickly as the dozen or so rescue workers were able to find and carry them.

"We have found 50 bodies today and there'll be more," said an officer in the self defence forces as his team took a quick lunchbreak. "We're putting more efforts into rescue elsewhere as there is very little chance of anyone surviving here."

11.54am: Associated Press has this report from Banda Aceh in Indonesia of the reactions of survivors of the 2004 tsunami watching the pictures of the devastation in Japan:

Tears streamed down Maisara Mucharam's face as she watched aerial shots of the tsunami pummeling Japan's coast and remembered the day, six years ago, when her youngest daughter was ripped out of her arms by the heavy salty sea.

Survivors of the 2004 tsunami that started off Indonesia sat glued to their TV sets, stroking each other's hands, as images of last Friday's disaster in northern Japan flashed repeatedly across the screen.

"I heard someone screaming and ran to see what was going on," said Mucharam, who also lost her husband and two other daughters.

"I tried, but couldn't stop watching," the 38-year-old said, her voice trembling. "It was exactly the same, except they have this horrible footage, events unfolding right before your eyes."

•The struggle to control a nuclear crisis at two power stations continues. Officials said there is a risk of a second explosion at the Fukushima power station but Yukio Edano, chief cabinet secretary, said the facility could withstand the impact. Technicians are battling to cool a third reactor after a blast at reactor one on Saturday. Technicians are pumping sea water into the reactor in a bid to prevent a nuclear meltdown. The size of the evacuation zone around Fukushima is now 20km.

•The Japanese prime minister has called the disaster the worst crisis since WWII. There are also reports that up to 10,000 are feared dead in the Miyagi prefecture alone and up to 190 people exposed to radiation after cooling system fails at a second nuclear plant.

•More than 250 aftershocks have rocked Japan since the original earthquake on Friday. The US Geological Survey said 30 of these were in excess of magnitude 6. Japan's meteorological agency said there was a 70% chance of a magnitude 7 aftershock striking in the next three days.

•The huge rescue effort now includes 100,000 Japanese soliders, around 40% of its armed forces. International rescue teams are heading towards the region including a UK team. Tokyo's vice-mayor said 44,000 meals of crackers, 643,000 of instant rice and 57,000 units of condensed milk are on their way to the disaster area, along with 384,000 blankets and 9000 portable toilets.

•Stories of rescues and tragedies are beginning to emerge, including from Hiromitsu Shinkawa, a 60-year-old man rescued after being swept out to sea with only his roof as a makeshift raft. Our correspondent Jonathan Watts in Miyagi prefecture interviewed Harumi Watanabe who said she was unable to rescue her elderly parents from their house before the wave hit.

•The UK Foreign Office has set up contact numbers for assistance for British nationals and has advised against all non-essential travel to Japan. It has also issued information about the status of Japanese airports.

1.02pm: My colleague Jo Adetunji has spoken to the Guardian's Asia environment correspondent Jonathan Watts who is in North East Japan. He said that in the city of Sendai there are huge queues for water, food and fuel.

1.11pm: Some analysis from Ian Sample about the crisis at the Fukushima nuclear power plants:

Guardian

The decision to pump sea water into the power station's No.1 reactor yesterday was unprecedented and it may be several days before engineers know whether the strategy has worked. The sea water, mixed with boric acid, should remove heat from the reactor and bring it within safe margins.

On Sunday, a similar technique was ordered at the station's No.3 unit, where a cooling system also failed. The reactors are usually cooled by deionised water, so pumping sea water around them will make them unusable in future.

On Saturday, a hydrogen explosion blew the roof off the No.1 reactor, injuring four workers. The hydrogen was produced when water inside the pressure vessel became superheated and split into hydrogen and oxygen. The hydrogen appears to have exploded when engineers vented pressure from the reactor.

Round up of reports from the affected area of North East Japan today from Jo Adetunji:

Reports have emerged of whole towns and villages swept away or submerged by the waves, including Rikuzentakata village in Iwate prefecture in which 5,000 houses have disappeared beneath the water.

In Otsuchi village, the town hall was swept away reportedly with the mayor and local officials inside. In Ofunato, a small northern coastal city, a nursing home with 30 elderly residents was swept away and rescuers in the town of Minamisanriku said they have been unable to locate half of the 17,500 population.

A ship that went missing after being swept away by the tsunami on Japan's northeastern coast on Friday was found and about 81 aboard were also airlifted to safety, Jiji Press said.

Professor Richard Wakeford from the Dalton Nuclear Institute at the University of Manchester explains more about the scale and response to the nuclear crisis.

The reactor cores were still hot when the reactor shut down (essentially when the chain reaction stops), as time goes on that radioactive decay heat will get less and the problem will get less. In this case, the diesel generators that ran the cooling systems were flooded by the tsunami, so sea water is now being used to cool the core.

"If the fuel is uncovered by cooling water it could become so hot it begins to melt – if all the fuel is uncovered you could get a large scale meltdown. So Japanese authorities are doing all they can at the moment to keep the core cooled with seawater.

"This is a well known potential accident scenario, so the regulatory authorities ensure that there are appropriate plans in place to ensure that cooling water is kept pumping. Ultimately in this case there was be provision to put seawater through the core to ensure that the core is covered and cooled.

"There will be intense monitoring around the site of the reactors for release of radiation. We will know immediately if there had been a major release – and this clearly hasn't happened at the moment.

"The Japanese authorities are doing the right thing by evacuating people just in case the worst happens. If it did, there are measures that will be taken – for example, to counteract radioactive iodine, people would be given stable iodine tablets that would block the uptake of radioactive iodine by the thyroid. They would also put out a food ban from the affected area.

"This approach is very different to Chernobyl where the authorities were in denial and did not act to protect the population (they did not issue iodine tablets or stop people eating local food) – many of the thyroid cancers seen could have been prevented by taking action immediately."

2.08pm: Ian Hanson, senior lecturer in forensic archaeology at Bournemouth University who is currently on sabbatical at the International Commission on Missing Persons, said the true numbers of those missing won't be accurate until all agencies involved in collecting data collate their information.

"Often with disaster situations numbers of people reported missing is very high initially – but this is often because multiple agencies are collecting information and individual missing people will be reported multiple times.

"We have seen this discrepancy before at 9/11- people were reported missing by multiple people to multiple agencies, and it is only once a united database of missing is collated that the true figure is known. 9/11 saw the number of missing drop rapidly from first days estimates of 20,000 to 10,000 then 5,000 ... then the true figure of just under 3,000 over time. We may see the same thing here as lists are amalgamated."

2.22pm: The US Geological Survey says the earthquake appears to have moved the main island of Japan by 2.4 metres. Kenneth Hudnut, a geophysicist, said:

"At this point, we know that one GPS station moved (8 feet), and we have seen a map from GSI (Geospatial Information Authority) in Japan showing the pattern of shift over a large area is consistent with about that much shift of the land mass."

Tsunami victim Hiromitsu Shinkawa,65, waves to rescuers who spotted him floating on the roof of his home more than seven miles out to sea. Photograph: AP

2.22pm: A picture of Hiromitsu Shinkawa, the man who was rescued by helicopter after he was swept away to sea on the roof of his house has emerged.

The aftermath of the explosion in the building housing reactor No 1 at the Fukushima nuclear power plant in Okuma, Japan. Photograph: Digitalglobe/Getty Images

2.47pm: Science correspondent Ian Sample has written a Q&A on the nuclear crisis at the Fukushima power plants. Here's a flavour:

The strategy of pumping sea water into nuclear reactors is untested. It could take several days to bring the temperature and pressure of the reactor cores down to within safe limits.

If the cooling fails, the reactors could overheat and cause a total meltdown of the radioactive fuel rods in the core. This would only lead to a major release of radiation if the reactor's containment vessel was breached.

The Japanese authorities have classified the sitiuation as a level 4 "accident with local consequences" on the International Nuclear and Radiological Event Scale (INES). The scale runs from zero for a deviation in normal operations to seven for a major accident. The Three Mile Island incident in 1979 was a five and Chernobyl in 1986 was a seven on the scale.

The rule of thumb for aftershocks is that you can expect a factor of about one magnitude less than the biggest shock. The other thing is 'Omori's law' - really an observation - that the rate of aftershocks decreases in a very predictable way.

The bigger the earthquake, the bigger the change in stress and the more aftershocks. There are many more aftershocks than after the Sichuan earthquake in China, but that was magnitude 7.9 and this was 8.9. You have 30 times more energy released. It's not about how much the ground shakes, but how much energy is released, because that's what gives other parts of the fault increased stress.

That's what aftershocks are: areas around [the location of the original shock] relieving stress. But those also affect other parts of the fault: you get a cascade effect.

On a positive note, he added that buildings should stand up to the strain. We see a cumulative effect with things like landslides: you weaken hill slopes, rock is shaken and a little bit loosened, and then the next shock – even if smaller – can trigger more landslides.

With buildings that tends not to happen. These [in Japan] are designed to move: they have expansion joints and shock absorbers…You are not creating cracks which get bigger and bigger. If they can survive the main shock they should be okay. The important thing is that they don't collapse, even if they are damaged: as long as they don't actually fall down, that's 95% of the battle.

3.02pm: Here's a live stream of NHK-TV. Lots of dramatic pictures of the tasunami aftermath and interviews with survivors.

3.10pm: The earthquake has bent the tip of the Tokyo Tower. This picture of the iconic landmark was taken by Martyn Williams, Tokyo bureau chief at IDG News Service.

3.36pm: According to Associated Press, Japan's weather agency says a volcano in southern Japan has resumed eruptions of ash. The Meteorological Agency issued a warning saying that Shinmoedake volcano had resumed shooting out gas, boulders and ash after a couple weeks of inactivity. The mountain is on the other side of Japan from the epicenter of Friday's magnitude 8.9 earthquake and resulting tsunami, which devastated much of the country's northeast coast. It was unclear if the eruptions were linked to quake.

4.17pm: Toyota has said it will suspend operations at all 12 factories in Japan on Monday. Nissan will also suspend production at its three domestic plants on Monday as two of them were damaged in the earthquake, with others set to follow according to autoblog UK.

Reuters is reporting that the Tokyo Stock Exchange and other Japanese financial markets will re-open on Monday as normal, the government said. Financial Services Minister Shozaburo Jimi said in a statement that authorities would watch market activity closely to ensure against market manipulation in the wake of the disaster.

An official scans for signs of radiation on a woman in Nihonmatsu City in Fukushima Photograph: Yomiuri/REUTERS

4.30pm: More on the power shortages caused by the closure of nuclear plants:

Tokyo and the surrounding area will see rolling three hour blackouts from tomorrow, officials have said. Schedules are still being finalised and the measures could apply for weeks. "We have to avoid at all costs a sudden power shortage whose scale could have devastating consequences for the economy and people's lives," Prime Minister Naoto Kan told a press conference.

@TimeOutTokyo says NHK is reporting a government request for residents to avoid going to work tomorrow, if possible, to relieve expected pandemonium at stations.

•The original earthquake to hit Japan has been upgraded to a magnitude of 9.0 by the Japanese authorities (the US Geological Survey has not made the same change).

•The struggle to control a nuclear crisis at two power stations continues. Officials said there is a risk of a second explosion at the Fukushima power station but Yukio Edano, chief cabinet secretary, said the facility could withstand the impact. Technicians are battling to cool a third reactor after a blast at reactor one on Saturday. Technicians are pumping sea water into the reactor in a bid to prevent a nuclear meltdown. There are also unconfirmed reports that a cooling system pump has stopped operating at Tokai No. 2 Power Station, a nuclear power plant, in the village of Tokai, Ibaraki Prefecture.

•More than 250 aftershocks have rocked Japan since the original earthquake on Friday. The US Geological Survey said 30 of these were in excess of magnitude 6. Japan's meteorological agency said there was a 70% chance of a magnitude 7 aftershock striking in the next three days.

•The huge rescue effort now includes 100,000 Japanese soliders, around 40% of its armed forces. International rescue teams are heading towards the region including a UK team. Tokyo's vice-mayor said 44,000 meals of crackers, 643,000 of instant rice and 57,000 units of condensed milk are on their way to the disaster area, along with 384,000 blankets and 9000 portable toilets.

•Stories of rescues and tragedies are beginning to emerge, including from Hiromitsu Shinkawa, a 60-year-old man rescued after being swept out to sea with only his roof as a makeshift raft.

6.00pm: Good evening. This is Richard Barnes continuing our live coverage.

Concern is growing over "inevitable" British casualties caught up in the devastating Japanese earthquake and tsunami. Two days on from the disaster, the Foreign Office said there were no confirmed casualties from the UK, but they have received more than 4,000 calls from worried loved-ones according to the Press Association:

Around 17,000 British nationals were believed to be living and working in Japan when the catastrophic quake struck at 5.46am (GMT) on Friday.

English teacher Jenny Tamura Spragg, 33, who lives in Saitama, described how people were queueing for miles for petrol, shops were selling out of basic food and power saving cuts were being introduced.

"Supermarkets have sold out of rice, bread, milk, bottled water and other daily necessities as people stock up out of precaution or fear that another big one will hit. As far as British expats' safety is concerned, I would say that British casualties are an inevitable reality."

Back in the UK, Foreign Office minister Jeremy Browne said there would "almost certainly" be foreigners affected. He told Sky News: "I am not in a position to make a definitive statement about the number of British nationals caught up in it but clearly it is a huge devastating disaster and there almost certainly will be foreign nationals involved."

In other British related news, Chris Huhne, the energy secretary, said he has asked British regulators to study the Japanese situation to "learn any lessons" for UK power stations.

Save the Children have launched a £1 million appeal to help families affected by the devastating Japanese earthquake and tsunami. They have a team in Japan heading to Sendai – the city closest to the epicenter – and are developing a response plan to the disaster. If you would like to contribute or have more details, please do visit their appeal website.

6.17pm: More details are beginning to emerge about the breakdown of one of two cooling systems pumps at Tokai No. 2 nuclear power plant in the village of Tokai, Ibaraki prefecture.

The Japan Times says that a report submitted to the Ibaraki prefecture government has confirmed that one of two pumps used to cool the water of a suppression pool for the nuclear reactor has stopped working. The other pump is still working though, and Japan Atomic Power has said the reactor core is being cooled without any problem.

Members of Japan Self-Defense Forces rescue people stranded at a flooded city center in Ishinomaki, Miyagi prefecture on Sunday. Photograph: AP/Kyodo News

And above, just one of the many photographs coming out of Miyagi prefecture that are beginning to give an indication of the extent of the devastation in that part of Japan.

6.59pm: And staying on the photographic front for a moment, the New York Times has produced a "before and after" interactive that really does help to bring home the scale of the destruction.

7.22pm: The Japanese ambassador to the UK, Keiichi Hayashi, has just been interviewed on Sky News. He says he did not want to speculate on the specific numbers of dead, but would rather focus upon the search and rescue operation.

He estimated that up to 100,000 people will need to be rescued, and says the Japanese government has mobilised emergency services who are very well trained in disaster relief. The longer-term plans will be diverted to rebuilding destroyed infrastructure and taking care of the living.

He says of the Fukushima nuclear emergencies at Unit 1 and Unit 3 he cannot say whether or not there has been any kind of meltdown, but appropriate measures have been taken. He reassures that the Japanese government will be sharing information as much as possible and ensuring transparency over the incidents.

Regarding the slow response of the Japanese government to international offers of help, he says that they needed to assess the situation and decide what was needed first.

He praises the calm response of the Japanese people – "no riots, no looting" – and says with that kind of spirit he is sure the country can deal with the crisis.

Peter Yanev, one of the world's best-known consultants on designing nuclear plants to withstand earthquakes, said the seawalls at the Japanese plants could not handle tsunami waves of the height that struck them. But the diesel generators were situated in a low spot on the assumption that the walls were high enough to protect against any likely tsunami.

That turned out to be a fatal miscalculation. The tsunami walls either should have been built higher, or the generators should have been place on higher ground to withstand potential flooding, he said. Increasing the height of tsunami walls, he said, is the obvious answer in the immediate term.

"The cost is peanuts compared to what is happening," he said.

7.39pm: The latest Tokyo Electric Power Company press release provides some more details about the current plant status of the Fukushima Daiichi nuclear power station, including information about casualties at the plant and what actions are currently being taken.

That they are issuing regular updates such as this is perhaps an example of the transparency which the Japanese ambassador to the UK spoke of earlier.

Reporting that there has been little respite for survivors in Japan, Tana Branigan says that 30 of the hundreds of aftershocks that have continued to batter the coast since the main quake have measured more than magnitude 6. The country's meteorological agency has warned that there is a 70% possibility of a tremor of magnitude 7 or higher in the next three days, and a 50% risk in subsequent days.

The wave from a tsunami crashes over a street in Miyako City, Iwate Prefecture in northeastern Japan. Photograph: HO/Reuters

And above, a picture of the tsunami as it hits the shoreline that will be appearing in tomorrow's paper:

8.28pm: "The bodies just keep coming ..."

Sorry, your browser is unable to play this video.

The Guardian's Jonathan Watts is currently in Miyagi prefecture and reports in this video shot by Dan Chung on the destruction wrought by the tsunami.

9.40pm: In the wake of the Japanese earthquake and tsunami, environmental pressure groups are calling on governments in other vulnerable countries to abandon new nuclear power stations and large waste dump projects or greatly raise safety standards, reports the Guardian's John Vidal.

According to the Vienna-based International Atomic Energy Authority, 20% of the world's 442 working commercial nuclear power stations are in areas of "significant" seismic activity. With the nuclear industry hoping to build 350 new reactors within 20 years to meet soaring electricity demand and to counter climate change, the risk of a nuclear catastrophe from a natural disaster is growing significantly, they say.

9.51pm: The full extent of the economic impact of Friday's earthquake and tsunami is becoming apparent, reports Tim Webb.

With hundreds of factories shut across Japan, warnings of rolling blackouts and predictions from economists that the disaster would push the country into recession.

The Bank of Japan is preparing to pump billions of yen into the economy when it announces an emergency "quake budget" on Monday to prevent the disaster derailing the country's fragile economic recovery.

Japanese authorities have informed the IAEA that radioactivity levels at the site boundary of the Onagawa nuclear power plant have returned down to normal background levels. The first (ie lowest) state of emergency was reported at the plant earlier on Sunday after an increased level of radioactivity was detected at the site boundary. Investigations at the site indicate that no emissions of radioactivity have occurred from any of the three units at Onagawa. The current assumption of the Japanese authorities is that the increased level may have been due to a release of radioactive material from the Fukushima Daiichi nuclear power plant.

The IAEA continues to liaise with the Japanese authorities and is monitoring the situation as it evolves.

10.12pm: Back to the anxious wait for UK relatives of people who may have been caught up in events in Japan. Ben Quinn reports on the latest situation:

Britons who are unaccounted for include Brian Hickebottom, 34, who is missing with his Japanese wife and their six-month-old daughter.

They live seven miles from Sendai in the coastal city of Tagajo – the worst-hit area of the disaster. His family in Britain hope that they are in shelter. "We are all extremely worried. We have spoken to a few people but still haven't heard anything," said his sister, Emma Hickebottom.

"It looks like it was right were they live and it's more worrying as Brian would have been at work and Sanae at home. I hate to think they're separate. It's starting to be become very tough for everyone and we just want them all to be okay.

"Mum and dad were planning to fly out and visit him in a couple of weeks because they haven't met their grand-daughter Erin yet."

Originally from Birmingham, West Midlands, Mr Hickebottom has lived in Japan for three years and teaches English in schools.

Japan is proud of having the world's longest life expectancy, which is particularly evident in rural areas. Shintona's large elderly population is evident in the intimate belongings now scattered in the muddy streets – 12-inch vinyl albums of Enka (Japanese blues) classics, a walking stick and tatami mats.

This community is home to one of Miyagi's first old people's homes. The care manager, Kiyoko Kawanami, said she was able to confirm only 20 of the 90 residents as safe. "We don't know what happened to them. The tsunami hit while we were trying to organise an evacuation," she said.

Kawanami took one group to the emergency shelter in Nobiru primary school. "On the way back I was stuck in traffic. There was an alarm. People screamed at me to get out of the car and run uphill. It saved me. My feet got wet but nothing else."

The fate of the other residents remains unclear. Shigejiro Murayama had come to look for his lost brother. While his wife cried and sighed beside him, he silently progressed as quickly as he was able with a walking stick. But he had to turn back when he saw what had happened.

"There is no road left," he laughed darkly. "This is a mess. Look at what has happened."

I am writing this text (Mar 12 ) to give you some peace of mind regarding some of the troubles in Japan, that is the safety of Japan's nuclear reactors. Up front, the situation is serious, but under control. And this text is long! But you will know more about nuclear power plants after reading it than all journalists on this planet put together.

11.28pm: A colleague has sent a link here to an extraordinary six minute amateur video that starts slowly, with the tsunami as only a trickle, and builds to show its immense destructive force.

Currently trying to find out more information about where it's from and who shot it.

11.39pm: A little more information on the video link posted below. It shows the tsunami sweeping through Kesennuma, a city located in the extreme north-east of Miyagi prefecture in Japan.

11.54pm: A story from the Japanese paper, the Yomiuri Shimbun has experts saying that "tsunami overlap" increased its destructive power.

The multiple tsunami caused by Friday's Tohoku Pacific offshore earthquake wreaked enormous destruction not only because of the quake's massive energy and proximity but also because they hit coastal areas from various angles and overlapped, experts said.

As the fault rupture was 310 miles (500 km) long in a north-south direction, "tidal waves hit the coastal area from different directions and crossed over each other, increasing [the tsunami's] destructive power," said Tomoya Shibayama, professor of ocean engineering at Waseda University. "They also became higher after currents threw them back and forth against the sea floor in coastal areas where the water was more shallow."

For residents of Ofunato, Iwate prefecture, and the Sanriku coast in Kesennuma, Miyagi prefecture, it is common knowledge to quickly evacuate when tsunami warnings are given because the areas have experienced massive tidal waves many times before.

Nonetheless, damage this time was catastrophic because the latest tsunamis were higher and faster than expected. If a tsunami was four metres high, its approaching speed would have been 21 km per hour, experts said.

12.11am: The Nikkei market has just opened in Japan for the first full day since the earthquake struck on Friday. In early trading shares have fallen about 2%, roughly in line with what analysts were predicting.

There are concerns about the financial hit the country will have to take as it rebuilds its infrastructure.

12.35am: Wrapping up the live blog for now. A brief round up of events: